If the wheel had not been re-invented then they would still be made of wood!
As for the 'futility' of getting data over a noisy DC line the problems are not beyond a solution, indeed if anything many real world examples of 'fly-by-wire' can be found not only in aviation but automotive applications.
Closer to home some manufactures of traffic control systems, both temporary systems used during road works and permanent installations communicate both sensor and control data over the DC power line. If you think an automotive DC power line is a bit 'Rough' the you should see what the output of a beat up generator looks like
Sticking with in-car applications a quick search of the web reveals a nifty idea to use the DC power line to inter-connect the various elements of 'ICE' (In Car Entertainment) no rolls of wire for the speakers or getting under the dashboard to run the control head cable back to the CD changer in the trunk. Just put the hardware where you want it and find a live wire.